torch.unravel_index

torch.unravel_index(indices, shape)

Converts a tensor of flat indices into a tuple of coordinate tensors that index into an arbitrary tensor of the specified shape.

Parameters

• indices (Tensor) – An integer tensor containing indices into the flattened version of an arbitrary tensor of shape shape. All elements must be in the range [0, prod(shape) - 1].

• shape (int, sequence of ints, or torch.Size) – The shape of the arbitrary tensor. All elements must be non-negative.

Returns

Each i-th tensor in the ouput corresponds with dimension i of shape. Each tensor has the same shape as indices and contains one index into dimension i for each of the flat indices given by indices.

Return type

tuple of Tensors

Example:

>>> import torch
>>> torch.unravel_index(torch.tensor(4), (3, 2))
(tensor(2),
 tensor(0))

>>> torch.unravel_index(torch.tensor([4, 1]), (3, 2))
(tensor([2, 0]),
 tensor([0, 1]))

>>> torch.unravel_index(torch.tensor([0, 1, 2, 3, 4, 5]), (3, 2))
(tensor([0, 0, 1, 1, 2, 2]),
 tensor([0, 1, 0, 1, 0, 1]))

>>> torch.unravel_index(torch.tensor([1234, 5678]), (10, 10, 10, 10))
(tensor([1, 5]),
 tensor([2, 6]),
 tensor([3, 7]),
 tensor([4, 8]))

>>> torch.unravel_index(torch.tensor([[1234], [5678]]), (10, 10, 10, 10))
(tensor([[1], [5]]),
 tensor([[2], [6]]),
 tensor([[3], [7]]),
 tensor([[4], [8]]))

>>> torch.unravel_index(torch.tensor([[1234], [5678]]), (100, 100))
(tensor([[12], [56]]),
 tensor([[34], [78]]))